The structure of polymer chain of poly(1,3-pentadiene) synthesized via a stereospecific polymerization catalyzed by a system based on neodymium trichloride was determined using one-dimensional with a T₂ filter and two-dimensional HMBC and HSQC ¹H-¹³C NMR spectroscopic methods. It was found that the polymer chain of poly(1,3-pentadiene) consists of 1,4-trans-, 1,4-cis-, 1,2-trans-, and 1,2-cis-units. A new method was proposed for the quantitative calculation of content of the structural units in poly(1,3-pentadiene) possessing a mixed microstructure. Spectral signals of the carbon atoms of terminal units having 1,4-trans- and 1,4-cis-structures have been for the first time identified in the macromolecules of poly(1,3-pentadiene) synthesized via the stereospecific polymerization.